This project investigates the biochemistry of dopamine receptors. Using the insight gained about the biochemical basis of dopamine receptor function, drugs selectively interacting with the various subcategories of dopamine receptor are identified and characterized. The availability of drugs selectively stimulating or blocking the various subcategories of dopamine receptor will be useful in the treatment of Parkinson's disease, endocrine disorders, psychiatric disorders, hypertension and as antiemetics in cancer chemotherapy. Among the topics studied during the current fiscal year are: binding of spiroperidol to the D-2 dopamine receptor in the intermediate lobe of the rat pituitary gland; characterizing the D-2 dopamine receptor regulating acetylcholine release and cyclic AMP synthesis in the striatum; identifying YM-09151-2 as a selective D-2 antagonist; identifying the coordinated role of calcium ions and cyclic AMP in the intermediate lobe of the rat pituitary gland and investigating the hypothesis that drugs can discriminate between the pre- and postsynaptic dopamine receptors.